Evidence of an Ozone Mini-Hole Structure in the Early Hunga Tonga Plume Above the Indian Ocean

Abstract. On 15 January 2022, the Hunga Tonga-Hunga Ha’apai (HTHH) volcano (20.5° S, 175.4° E) erupted, releasing significant amounts of aerosols, sulfur dioxide (SO₂), and water vapor (H₂O) into the stratosphere. Due to the general stratospheric circulation of the southern hemisphere, this volcanic plume traveled westward and impacted the Indian Ocean and Reunion (21.1° S, 55.5° E) a few days after the eruption. This study aims to show how the currently available ozone observations highlight the stratospheric dynamics during the first week following the eruption. The Ozone Mapping and Profiler Suite Limb Profiler (OMPS-LP) aerosol extinction profiles were used to investigate the vertical and latitudinal extension of the volcanic plume over the Indian Ocean. The volcanic aerosol plume was also observed with an aerosol lidar and a sunphotometer located at Reunion. The impact of this plume on stratospheric ozone was then investigated using MLS (Microwave Limb Spectrometer), OMI (Ozone Monitoring Instrument), MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, version 2) and M2-SCREAM (MERRA-2 Stratospheric Composition Reanalysis of Aura MLS) ozone profiles and total ozone. The results show that the volcanic plume traveled over Reunion at altitudes ranging from 26.8 to 29.7 km and spanned more than 20 degrees of latitude over the Indian Ocean. Ozone analyses reveal an ozone mini-hole structure, with the Total Column Ozone (TCO) anomaly of -15 DU from MERRA-2 covering an area of 12.06×10⁵ km² on 17 January and 4.94 × 10⁵ km² on 22 January. The ozone profiles from MLS show that a maximum stratospheric column ozone anomaly of -14.66 DU (-6.38 %) was found within the aerosol plume on 20 January.